The Oil Light on my 02 Ranger 4x4 TD takes about three seconds to extinguish when cold. After an immediate restart it's almost instantaneous but after thirty minutes it again takes about three seconds to go out.The engine is very healthy, has covered 128,000 miles, doesn't smoke, rattle or use any oil and is extremely clean plus it always starts instantly.Do genuine oil filters have a non-return valve so that they don't drain out and could that the be the problem as I'm using god quality patterns?